/Engine/Plugins/Experimental/MeshModelingToolsetExp/Source/MeshModelingToolsExp/Public/Physics/CollisionGeometryVisualization.h
The FirstLineSetIndex parameter is used implement Settings->bRandomColors since random colors are determined using unique integers for each line set, which may be stored in separateUPreviewGeometryobjects. Since the update is partial this function doesn't check or set Settings->bVisualizationDirty, the caller should do that.
namespace UE { namespace PhysicsTools { void UE::PhysicsTools::PartiallyUpdateCollisionGeometryVisualization ( [UPreviewGeometry](API\Plugins\ModelingComponents\Drawing\UPreviewGeometry) * PartialPreviewGeom, [UCollisionGeometryVisualizationProperties](API\Plugins\MeshModelingToolsExp\Physics\UCollisionGeomet-) * Settings, int32 FirstLineSetIndex ) } }